A movable component of a piece of furniture such as a drawer of a desk, or a door of a wardrobe generates a loud bang when it slams shut with excessive force. Such noise is distracting and a nuisance. Sometimes, the same piece of furniture may even be damaged as a result of such forceful action. It is, therefore, desirable to shut a door or a drawer in a more controlled manner.
Previously, this has been accomplished by installing a totally sealed device having a piston to resist the motion of door shutting, but such devices are difficult to adjust in a predictable and controllable way.
Subsequently, European Patent Application EP 1236 925 A2 discloses a damper assembly for the use in connection with drawer slides, and doors for cupboards. The damper assembly comprises a cylinder of uniform bore adapted to receive a piston in a sealing engagement with the bore and to move axially of the bore, the piston being provided with a piston rod in sealing engagement with a bush acting to close one end of the bore, the opposite end being permanently closed. Part of the piston, termed as the piston ring by the inventor, is made of a resiliently deformable material which flattens under compressive force and the same part is pressed against the inner wall of the cylinder to provide frictional force during the inward stroke of the piston into the cylinder. However, the disadvantage of this sort of damper assembly is that the piston ring is highly prone to frictional wear and tear.
A better alternative is to use a hydraulic or fluidic damper. A hydraulic or fluidic damper normally has a cylindrical housing within which a piston is movable in a linear fashion. The same piston is attached to a form of mechanism for providing resistive force on the piston. The mechanism is usually a cylindrical block or a disc, which spans across the entire cross section of the cylinder with slight spatial allowance between the inner wall of the housing and the peripheral surface of the mechanism. The interior space of the housing is filled with a viscous fluid, so when the mechanism moves within the interior space, it experiences some degree of drag owing to its obstruction against fluid flow from one side of the mechanism to another. Unlike the previous damper described earlier, the mechanism is less susceptible to wear and tear since the inner wall of the housing is lubricated with the same viscous fluid that induces the drag force for the mechanism.
However, a conventional fluidic damper is designed to resist motion of both inward and outward stroke of the piston. To cater for the need to resist only motion of the inward stroke of the piston when the drawer is shutting but not the outward stroke, some modification needs to be done to the mechanism. It is precisely the objective of this invention as described in this patent.